Magnetic random access memory (MRAM) is known as one of memory elements using magnetoresistance effect elements. The MRAM includes a magnetic tunnel junction (MTJ) element using a tunnel magnetoresistance (TMR) effect as a memory element. The MRAM stores information, depending on the magnetized state of the MTJ element.
There are several types of MRAMs. One of them is spin injection MRAM. In the case of spin injection MRAM, information is written by causing current to flow directly in the MTJ element and by changing the magnetization direction of a free layer according to the direction of current.
When such an MTJ element is formed, the layers to be processed into a shape of the MTJ element are formed in sequence by sputtering method. Thereafter, each of the layers is processed by reactive ion etching (RIE) method.
The each layers is as follows when describing them from the bottom: a layer to be processed into a lower electrode, a layer to be processed into a first fixed layer (also called a pin layer), a layer to be processed into a first tunnel barrier layer, a layer to be processed into a free layer (also called a recording layer), a layer to be processed into a second tunnel barrier layer, a layer to be processed into a second fixed layer, and a layer to be processed into an upper electrode.
However, in the spin injection MRAM obtained by conventional method for forming the MTJ element, reduction of signal amount is observed and desired signal amount is not obtained.